I use categories and keyboard short cuts to organise the emails and then a processing routine that helps me blast through a busy inbox. You know how it is if you go away for a few days and don't check your emails, for example when I go on holiday I make a point of totally disconnecting from the internet and so can come back to a few hundred emails.
The general idea I use, just like in the link, is a GTD approach, anything I can delete (because I don't need to do anything with) I delete, anything that will take a little time to deal with I put to one side...
I also have rules that move messages into sub folders, this is a bit of a deviation from the standard 'have one inbox' approach of GTD, but it works for me. I use hotmail and have a few aliases which I use for different broad things... I have a junk@ address (and a rule that sticks those messages into a junk folder), I have an address for a martial arts class I teach and a rule that pushes emails into that mailbox folder. My goal is to keep my main inbox as clean as possible, so only emails that are for me stay in there. Then I check at 10am and 4pm and quickly blast through following a very similar approach to that in the linked answer.
I've got a good idea of where I'm getting a lot of emails from... a few key suspects, so in your case I'd just filter (just like @JoeBaker) to one of those domains and see how many messages there are. It's not a sophisticated approach, but then once you're on top of your inbox hopefully you shouldn't need to keep running a tool to find where you're getting the most traffic from. If you've really got a massive amount of email subscriptions then, IMO, picking on just one or two each time you check your emails / as and when they come in and deciding how to change dealing with them is a better approach than trying to fix all your subscriptions in one go.